The advancement of the optical fiber sensing (OFS) technology is strongly linked to the development of light sources, while lasers play a crucial role in determining the performances of OFS systems for diverse sensing applications. Over the past 15 years, the OFS group at the University of Electronic Science and Technology of China (UESTC) has focused on the OFS with various light sources. Here, we review the history of the OFS advancement at UESTC and conduct an in-depth examination of the sensing strategies involving advanced light sources and cutting-edge sensors. By employing single-frequency lasers (SFLs), multi-frequency lasers (MFLs), and optical frequency combs (OFCs) across various sensing scenarios, the research team reports a number of novel OFS devices and systems, and showcases their sensing capabilities from point sensors to distributed sensing, and sensor networks. We highlight the role of novel light sources, particularly integrated OFCs, in enhancing the OFS. Our findings show that OFCs, with outstanding merits of the ultrahigh coherence, broad bandwidth, ultrafast detectability, and multi-channel parallelism, can significantly improve the capabilities and performances of the OFS used for detecting both physical and biochemical parameters. To conclude, we provide a systematic overview of the OFS advancement at UESTC, with SFLs/MFLs, as well as OFCs, and discuss the technical challenges and prospects, as well as potential developments of the OFC empowered the OFS. Also, a roadmap is proposed for transitioning the OFCs-based OFS technology from laboratory settings to practical applications.

The performances of fiber-optic distributed acoustic sensing (DAS) systems are fundamentally limited by the trade-off between the sensing distance and response bandwidth (RB), constraining the effectiveness of the DAS for long-haul sensing applications greatly. To break such a limitation, this paper proposes a novel Zadoff-Chu (ZC) based nonlinear frequency modulation (ZC-NLFM) scheme that combines the zero-correlation property of the ZC method with the chirp diversity of NLFM. The generated ZC-NLFM pulses exhibit excellent sidelobe and inter-pulse interference suppression, enabling high-sensitivity DAS demodulation even under low signal-to-noise ratio conditions. Furthermore, by employing the large-effective-area fiber (LEAF) with the lower attenuation, higher stimulated Brillouin scattering threshold, and Raman amplification, a wide-frequency-range, long-distance, and low-noise DAS (WLL-DAS) with high strain sensitivity of 94.34 $\text{p}\mathsf{\epsilon }/\phantom{\text{p}\mathsf{\epsilon }\sqrt{\text{Hz}}}\sqrt{\text{Hz}}$ over a wide RB of up to 7 kHz and an ultralong sensing distance of 148 km at the spatial resolution of 10 m is achieved simultaneously. Compared to the conventional DAS, the proposed WLL-DAS achieves a 22-fold increase in the RB over an ultralong distance of >140 km, significantly extending the performance boundary and application range of the DAS.

Fiber-optic distributed acoustic sensing (DAS) offers a promising solution for continuous traffic monitoring; however, its widespread deployment is often hindered by poor signal quality, resulting in fragmented and faint vehicle trajectories. Existing techniques − including conventional signal processing and deep learning models − struggle to accurately reconstruct trajectories and estimate traffic parameters under such challenging conditions. To overcome these limitations, we propose the DAS-hierarchical vehicle estimation network (DAS-HiVENet), an end-to-end framework that fundamentally advances the state-of-the-art through three key innovations: a two-stage preprocessing pipeline for noise suppression and trajectory preservation; a novel generative adversarial network (GAN) with an enhanced U-shaped convolutional neural network (U-net) generator to reconstruct high-fidelity trajectories from degraded inputs; a rotated-you only look once (R-YOLO) detector using oriented bounding boxes to accurately detect slanted trajectories. Extensive field evaluations on multiple expressways confirm that it surpasses existing methods with breakthrough performance: a trajectory intersection over union (IoU) of 0.7076, vehicle counting detection rate of 96.7%, and speed estimation errors as low as 1.422 km/h for the mean absolute error (MAE) and 1.796% for the mean absolute percentage error (MAPE) over 30 minutes. Even in challenging bridge scenarios with severe trajectory adhesion, DAS-HiVENet maintains an over 96% detection rate and under 4% MAPE in speed estimation − significantly outperforming alternatives.

Brillouin optical time-domain reflectometry (BOTDR) is a key technique for distributed fiber sensing of strain and temperature, but performance is constrained by the inherently weak spontaneous Brillouin signal. Here, we propose and experimentally demonstrate a novel frequency- and time-division multiplexed BOTDR (FTDM-BOTDR) based on a frequency-stepped light source generated from a frequency-shifting loop. In contrast with existing multi-frequency BOTDR, Brillouin signals from all frequency channels are coherently detected with a single local oscillator (LO) light, maximizing LO power and thus the heterodyne gain for all channels simultaneously. Furthermore, the temporal interleaving of different pump frequencies avoids excessive Kerr nonlinearities. A theoretical model is developed to analyze the signal-to-noise ratio (SNR) in FTDM-BOTDR and illustrate how this single-LO configuration overcomes the SNR limit in conventional multi-frequency BOTDR systems. Using 13 frequency channels, the system achieves the Brillouin frequency shift (BFS) precision of 0.298 MHz at 10 km and a maximum sensing range of 70 km with a 40 ms acquisition time, representing a 3.3-fold precision improvement and a 30 km range extension compared to single-frequency BOTDR. This FTDM-BOTDR technique overcomes key performance bottlenecks of conventional BOTDR and provides a scalable pathway toward high-SNR, long-distance, and real-time distributed temperature or strain sensing.

In recent years, the fiber-optic distributed acoustic sensing (DAS) technology has played an important role in the oil and gas exploration and development. We develop an industrialized ultra-sensitive DAS instrument, named uDAS, which has world-class performances and robust engineering capability. The uDAS achieves the pε/√Hz level strain resolution and broadband frequency response from millihertz (mHz) to 10 kHz. The uDAS system has been widely applied to onshore and offshore vertical seismic profiling (VSP), hydraulic-fracturing monitoring, surface seismic exploration, near-surface structural investigation, and DAS-uphole, with deployments spanning all oilfields of China National Petroleum Corporation (CNPC), and part oilfields of Saudi Aramco and Abu Dhabi National Oil Company (ADNOC). In this paper, we introduce the key technologies of uDAS and its typical applications over the years. These applications demonstrate the uDAS’s ultrahigh sensitivity, broadband frequency response, and high fidelity, enabling near-wellbore fine imaging, high-resolution visualization of downhole fracturing processes, and production optimization. The uDAS is becoming the new generation of all-optical geophones to replace the conventional electronic geophone arrays.

Fiber-optic distributed acoustic sensing (DAS) has become a revolutionary technology in the field of acoustic/seismic wave detection as it has disruptive advantages over point acoustic/seismic sensors. Especially, DAS has found vital applications in oil/gas exploration and development. However, three-component DAS (3C-DAS) remains an unsolved bottleneck problem as the present DAS is only sensitive to the axial strain, limiting the application range of DAS greatly. Here, we proposed and verified the 3C-DAS concept based on the theory proposed. We processed signals from three independent optical fibers within a specially designed dual-sine-structured sensing cable to realize 3C-DAS. Field trials of the 3C-DAS units were completed outdoor and in the real oilfield, respectively, by using an ultra-sensitive DAS instrument developed. Furthermore, a 100 m-long 3C-DAS cable was designed, fabricated, and tested. The experimental results indicate that 3C-DAS has the statistically comparable signal-to-noise ratio and better imaging resolution due to higher spatial density when compared to electronic 3C geophones. This work pioneers the study of 3C-DAS and paves a way to develop a new generation of vector DAS systems, including 3C-DAS-based geophones, hydrophones, and sonars for imaging geophysical structures with higher fineness, detecting undersea targets with better resolution, and positioning aerial vehicles with higher accuracy.

This paper reviews a wide variety of fiber-optic microstructure (FOM) sensors, such as fiber Bragg grating (FBG) sensors, long-period fiber grating (LPFG) sensors, Fabry-Perot interferometer (FPI) sensors, Mach-Zehnder interferometer (MZI) sensors, Michelson interferometer (MI) sensors, and Sagnac interferometer (SI) sensors. Each FOM sensor has been introduced in the terms of structure types, fabrication methods, and their sensing applications. In addition, the sensing characteristics of different structures under the same type of FOM sensor are compared, and the sensing characteristics of the all FOM sensors, including advantages, disadvantages, and main sensing parameters, are summarized. We also discuss the future development of FOM sensors.

Phase-sensitive optical time domain reflectometry (Ф-OTDR) is an effective way to detect vibrations and acoustic waves with high sensitivity, by interrogating coherent Rayleigh backscattering light in sensing fiber. In particular, fiber-optic distributed acoustic sensing (DAS) based on the Ф-OTDR with phase demodulation has been extensively studied and widely used in intrusion detection, borehole seismic acquisition, structure health monitoring, etc., in recent years, with superior advantages such as long sensing range, fast response speed, wide sensing bandwidth, low operation cost and long service lifetime. Significant advances in research and development (R&D) of Ф-OTDR have been made since 2014. In this review, we present a historical review of Ф-OTDR and then summarize the recent progress of Ф-OTDR in the Fiber Optics Research Center (FORC) at University of Electronic Science and Technology of China (UESTC), which is the first group to carry out R&D of Ф-OTDR and invent ultra-sensitive DAS (uDAS) seismometer in China which is elected as one of the ten most significant technology advances of PetroChina in 2019. It can be seen that the Ф-OTDR/DAS technology is currently under its rapid development stage and would reach its climax in the next 5 years.

Single atomically thick graphene, with unique structural flexibility, surface sensitivity, and effective light-mater interaction, has shown exceptional advances in optoelectronics. It opens a door for diverse functionalized photonic devices, ranging from passive polarizers to active lasers and parametric oscillators. Among them, graphene-fiber biochemical sensors combine the merits of both graphene and fiber structures, demonstrating impressively high performances, such as single-molecule detectability and fast responsibility. These graphene-fiber biochemical sensors can offer tools in various applications, such as gas tracing, chemical analysis, and medical testing. In this paper, we review the emerging graphene-fiber biochemical sensors comprehensively, including the sensing principles, device fabrications, systematic implementations, and advanced applications. Finally, we summarize the state-of-the-art graphene-fiber biochemical sensors and put forward our outlooks on the development in the future.